Weird Dome Light Issues - Possible Bad Instrument Cluster?

[Spktyr]

Background:
My 2000 Limited V6 2WD has been doing very well in the current Texas heatwave – until last night. After running around town, I got home and upon exiting the vehicle I smelled what appeared to be burning plastic. I shut down and started checking around the vehicle with a light. I could not find any smoke or signs of flame and everything seemed to be working as it should (key in ignition chime, etc.) I went to the passenger side of the vehicle, opened the front passenger door, saw the dome light flicker a few times and then go out. I immediately pulled the battery ground and watched the truck for a while to make sure whatever was going on wasn’t going to set the truck on fire. This morning I went out and began troubleshooting.

I’m working off this wiring diagram:



What Works, What Doesn’t:
The dome light does not work in the “DOOR” setting, but works properly in “OFF” and “ON”.
The key-in-ignition chime and ignition ring light work properly and respond to door open/door closed as they should.
The factory RKE locks and beeps as normal with doors closed and does a long beep and refuses to do anything if the doors are open, as it should.
The sunroof, map lights and vanity mirror lights all work (they’re on the same circuit per the diagram).
The rear dome light works as it should in all three positions.
The ‘door open’ light on the instrument cluster does *not* come on.

What I’ve Done So Far:
I’ve done a visual inspection of the entire vehicle – there’s no obvious damage or melted anything. The burning smell may have been from some road debris or some silicone tape insulation that fell off the aftermarket trailer brake harness and hit the exhaust. I’ve checked all the fuses – there are no melted fuses or slots. All fuses are the correct factory spec and check out on a digital multimeter. I removed the front dome light and checked its function with a meter and a battery. It works to spec in all positions. I checked the two wires leading to the dome light. As I understand it from the diagram above, the blue with yellow stripe wire is supposed to carry battery voltage (+12V) and it does.



The other wire (light green with black stripe) is supposed to be a switched ground as far as I can tell. Turns out this also has battery voltage on it. At this point, the Texas heat chased me back inside.

What I Plan To Do:
In the morning, I am going to pull the instrument panel out and see if there’s any loose or burned connectors, then check the other end of the light green with black stripe wire to see if there’s some sort of short to power between the dome light and the instrument panel. Beyond that, I’m not sure what to do next.

Questions:
1. Does anyone have a troubleshooting guide or wiring diagram for the instrument panel itself?
2. Does anyone have any suggestions as to what could be the cause or where I should be looking?

Thanks for any assistance.

 

[brillo_76]

You Said something about the trailer hitch woring hitting the exhaust. That could have been your burning smelling plastic.

I have seen 3rd gen lights flicker from the bulb itself and from warn door switches.

The ground is coming from the screwes. So your 2 wires are the following. 1 is the constant 12v the other is from the door switches. So in the off posiition no positive is connected.. On the on position the gnd and positive are connected and if the bulb is good the light is on.

Other door position, any of the 4 doors switches in a normally open position. So when you open a door if the switches are working properly. They complete the [ normally closed] position] wire and the light comes on.


I suspect that you have one of 2 things going on.


1] the contacts on the switch is oxidized in the door position and it's not making contact in the Door position.

2] One or more door switches are bad.


Being when you open any of the 4 doors and the light isn't working. I would suspect the contact on the light switch is oxidized abd not making contact when in the Door position.


Instrument lights can burn at any time. Being all 3rd gebs are 20 years and older. It's possible it's burned out but can easily be checked with a meter.

Just some thoughts hopes it helps.




Sent from my SM-A505U using Tapatalk

 

[Skulking]

This post has a link to the full wiring diagram which should include the combination meter (Instrument panel).

 

[Skulking]

You Said something about the trailer hitch woring hitting the exhaust. That could have been your burning smelling plastic.

I have seen 3rd gen lights flicker from the bulb itself and from warn door switches.

The ground is coming from the screwes. So your 2 wires are the following. 1 is the constant 12v the other is from the door switches. So in the off posiition no positive is connected.. On the on position the gnd and positive are connected and if the bulb is good the light is on.

Other door position, any of the 4 doors switches in a normally open position. So when you open a door if the switches are working properly. They complete the [ normally closed] position] wire and the light comes on.


I suspect that you have one of 2 things going on.


1] the contacts on the switch is oxidized in the door position and it's not making contact in the Door position.

2] One or more door switches are bad.


Being when you open any of the 4 doors and the light isn't working. I would suspect the contact on the light switch is oxidized abd not making contact when in the Door position.


Instrument lights can burn at any time. Being all 3rd gebs are 20 years and older. It's possible it's burned out but can easily be checked with a meter.

Just some thoughts hopes it helps.




Sent from my SM-A505U using Tapatalk

It is a switched ground, not a switched 12v. In the On position the switch grounds to the screws into the body. In the off position the 12v is still there but there is no ground connection. In the door position the black and green wire is either connected to ground or not depending on the door switches which runs through the combination meter.

From the steps given so far it is unclear if light and fob locking has been tested individually for all of the doors or not. If the doors have all been tested individually and the light doesn't come on for any of them individually, and the fob won't lock the car if any individual door is open, then the door switches are working properly which means they are not the source of the problem.

 

[brillo_76]

It is a switched ground, not a switched 12v. In the On position the switch grounds to the screws into the body. In the off position the 12v is still there but there is no ground connection. In the door position the black and green wire is either connected to ground or not depending on the door switches which runs through the combination meter.



From the steps given so far it is unclear if light and fob locking has been tested individually for all of the doors or not. If the doors have all been tested individually and the light doesn't come on for any of them individually, and the fob won't lock the car if any individual door is open, then the door switches are working properly which means they are not the source of the problem.

Ah. I had it reversed. Thanks for the correction. makes more sense to switch the ground.

Sent from my SM-A505U using Tapatalk

 

[Spktyr]

From the steps given so far it is unclear if light and fob locking has been tested individually for all of the doors or not. If the doors have all been tested individually and the light doesn't come on for any of them individually, and the fob won't lock the car if any individual door is open, then the door switches are working properly which means they are not the source of the problem.

Light has been tested for all doors individually and does not come on for any of them. Remote locking has been tested for the front two doors (forgot to do the rears) and it will not lock with either front door open - it makes the long 'error' beep.

This post has a link to the full wiring diagram which should include the combination meter (Instrument panel).

I did already have that, but it looks like all of it goes into a "white box" and there doesn't seem to be any documentation in the manual on the contents or logic of the "white box". Is it possible that the unit has decided to switch power into what's supposed to be a ground?

 

[brillo_76]

Light has been tested for all doors individually and does not come on for any of them. Remote locking has been tested for the front two doors (forgot to do the rears) and it will not lock with either front door open - it makes the long 'error' beep.




I did already have that, but it looks like all of it goes into a "white box" and there doesn't seem to be any documentation in the manual on the contents or logic of the "white box". Is it possible that the unit has decided to switch power into what's supposed to be a ground?

I would think that if for some reason you have a short a fuse would blow.

Sent from my SM-A505U using Tapatalk

 

[Skulking]

Light has been tested for all doors individually and does not come on for any of them. Remote locking has been tested for the front two doors (forgot to do the rears) and it will not lock with either front door open - it makes the long 'error' beep.




I did already have that, but it looks like all of it goes into a "white box" and there doesn't seem to be any documentation in the manual on the contents or logic of the "white box". Is it possible that the unit has decided to switch power into what's supposed to be a ground?

The white box is the combination meter which is page 228. That doesn't help much beyond what you already have on the diagram for the interior light though. There isn't sort of programmable logic driving things here, it's all electrical so nothing has decided to put 12v on the wrong wire.

The black and green wire you have 12v on but should be ground runs from the roof down to the drivers side junction box by your left knee and in plug 1A pin 7. It then runs out plug 1H pin 2 (both locations shown on page 24) to go to the combination meter on C27 pin 13 (picture on page 262). Those are going to be the places to easily check for signs of shorting, and also the places you can try and figure out which section of that run is actually picking up the power.

Page 25 does also show that plug 1D pin 2 is connected to the circuit in the junction box, but I've not yet been able to figure out what that is actually connected to from there.

Edit: The overall EWD doesn't show any connections on plug 1D pin 2 or 8 even though the relay section on page 25 does show that plug 1 D pin 2 connects with plug 1A pin 7 and plug 1H pin 2 in the drivers side junction box. It's probably worth checking what is happening in the actual wiring there. The most likely answer is that there isn't a wire connected to the pin so it doesn't really matter, but it is something else to verify.

 

[Spktyr]

I would think that if for some reason you have a short a fuse would blow.

Almost all the lights (dome and instrument) in my truck were replaced years ago with LEDs - the diode function of the LEDs may be why I'm not blowing fuses despite power trying to go where it's not supposed to.

The white box is the combination meter which is page 228. That doesn't help much beyond what you already have on the diagram for the interior light though. There isn't sort of programmable logic driving things here, it's all electrical so nothing has decided to put 12v on the wrong wire.

Okay, so there's no switching or anything else at all on this line?

The black and green wire you have 12v on but should be ground runs from the roof down to the drivers side junction box by your left knee and in plug 1A pin 7. It then runs out plug 1H pin 2 (both locations shown on page 24) to go to the combination meter on C27 pin 13 (picture on page 262). Those are going to be the places to easily check for signs of shorting, and also the places you can try and figure out which section of that run is actually picking up the power.

Page 25 does also show that plug 1D pin 2 is connected to the circuit in the junction box, but I've not yet been able to figure out what that is actually connected to from there.

Edit: The overall EWD doesn't show any connections on plug 1D pin 2 or 8 even though the relay section on page 25 does show that plug 1 D pin 2 connects with plug 1A pin 7 and plug 1H pin 2 in the drivers side junction box. It's probably worth checking what is happening in the actual wiring there. The most likely answer is that there isn't a wire connected to the pin so it doesn't really matter, but it is something else to verify.

I actually have a spare (bad odometer display) instrument cluster here, so I may play with that.

My thought is that the most efficient way to troubleshoot is to start by pulling the instrument cluster, pulling C27 and seeing if that light green/black wire at the dome light loses power. If it does, I'm thinking that indicates there's something wrong with the instrument cluster. If not, I can work my way back upstream from there through the junctions you list. Thoughts on this?

 

[Skulking]

Almost all the lights (dome and instrument) in my truck were replaced years ago with LEDs - the diode function of the LEDs may be why I'm not blowing fuses despite power trying to go where it's not supposed to.



Okay, so there's no switching or anything else at all on this line?



I actually have a spare (bad odometer display) instrument cluster here, so I may play with that.

My thought is that the most efficient way to troubleshoot is to start by pulling the instrument cluster, pulling C27 and seeing if that light green/black wire at the dome light loses power. If it does, I'm thinking that indicates there's something wrong with the instrument cluster. If not, I can work my way back upstream from there through the junctions you list. Thoughts on this?

Based on my experience accessing the instrument cluster plugs is definitely easier that accessing the junction box plugs. Beyond that you are starting to get into things I'm much more fuzzy on. What you suggested makes sense, but someone mare familiar with electrical systems may be able to answer with more confidence what the behavior should be.

 

[brillo_76]

The only issues I had with dome lights in over 30 years hobby mechanicing on them. Was oxidized switch and bad door switches. With a switch or bulb going bad. Now this was with the standard bulbs in the cucuits.

The flickering in my instances, was a door switch failing or the bulb element just about ready to burn out.

That was it. In camrys, pickup trucks, Tacoma which all had the button switches with the 3 position switch.

Led can burn out as well. But this isn't the case as your dome light works in the on position.

If you checked every door switch and they have continuity when they are supposed to. That should eliminate them.

If the led is good in the instrument cluster. Your running out options. As I personally never seen a dome light cucuit fail due to wire issues. However, that's me in my experiences.



Sent from my SM-A505U using Tapatalk

 

[Skulking]

The only issues I had with dome lights in over 30 years hobby mechanicing on them. Was oxidized switch and bad door switches. With a switch or bulb going bad. Now this was with the standard bulbs in the cucuits.

The flickering in my instances, was a door switch failing or the bulb element just about ready to burn out.

That was it. In camrys, pickup trucks, Tacoma which all had the button switches with the 3 position switch.

Led can burn out as well. But this isn't the case as your dome light works in the on position.

If you checked every door switch and they have continuity when they are supposed to. That should eliminate them.

If the led is good in the instrument cluster. Your running out options. As I personally never seen a dome light cucuit fail due to wire issues. However, that's me in my experiences.



Sent from my SM-A505U using Tapatalk

There's a good suggestion in there. We're currently assuming that the 12v shouldn't be present on the black and green wire (I'm fairly certain this is true), but checking the switch on the light for continuity in the door position is going to be by far the easiest thing you can check which you haven't already looked at.

 

[brillo_76]

I had a few domes not working over the years. Just stopped one day worked when switch to on. Cleaned the contacts on the switch and it worked again. The copper in on the switched was too tarnished from always being in the on position.

How I quick found it was switching the switch into the 3 positions and back out like 10x with the door open. When it flickered once I knew it was a bad switch. Copper opposed to air tarnishes and if enough tarnish builds up the resistance increases and there isn't 12volt going to the dome light anymore.

I would with the meter probes on the light socket.

On would be 12 volts as the dome light works.


In the door position, according to other members it's switched ground coming in.

If this is correct, any door open should be sending the ground to the light and turning it on.

Plus with all doors shut that same wire should be open.

Thus no light because it isn't a complete circuit.

At some point I test one of mine to verify..

Sent from my SM-A505U using Tapatalk

 

[Spktyr]

I found the source of the burning smell that wasn't going away.


IMG_7591


IMG_7595


IMG_7607


IMG_7608


IMG_7615


IMG_7620

 

[brillo_76]

Instrument cluster meltdown. Can't say I seen that before.. Interesting.

At least you found it.

Sent from my SM-A505U using Tapatalk

 

[SaulG]

C27 connector looks to be interior lighting feeds, exterior and headlamps..?

 

[Spktyr]

C27 connector looks to be interior lighting feeds, exterior and headlamps..?

Well, the first sign of something going wrong (other than the smell of something burning/smoldering) was the dome light flickering and going out.

I've got a few decades of experience with British cars, going back to childhood. I know exactly what "I smell something burning" and "Hey, that part of the electrical system just flickered and went offline" means. It means "Disconnect your battery and shut down your electrical system *now* because you're about to have an electrical fire if you don't already."

(Not my car, not my pic, just using as an example.)

Generally the rule with British cars is that once you've got everything safed and you've waited to see if something smoldering behind cover is going to burst into flames, the next step is to start tracing things back from the system you saw fail. The fact that the burning appears to around some diodes that are in the 4Runner's lighting circuit seems to make sense in this context.

 

[brillo_76]

Yes.. you been around... Dash flickering bad. I just seen oxidation in the dome overhead light due the same flickering. Only with standard bulbs though. Very interesting possibilities on the leds. As they would stop current flow in the opposite direction.

Still should have blown the fuse if it melted down. The cucuit amperage should have been exceeded and snapped that fuse open. Very odd indeed and as far as I know, hasn't been reported as happening before on this forum...:/

Sent from my SM-A505U using Tapatalk

 

[Spktyr]

The harness connector had some congealed smoke/fumes on it, but was undamaged.


IMG_7654

Checked out the wiring harness - with the instrument cluster removed, the wire read 0V as expected at both ends with a digital multimeter.


IMG_7651

After eliminating the harness as the source of the problem, I went to the burned gauge pod and found/confirmed with the DMM that the D24 diode had gone bad; it had decided to no longer be one way.


IMG_7662

Figured out why my spare cluster had display issues with the LCD odometer (loose cables) and swapped that in... after checking the D23, D24 and D25 diodes were still working with the DMM. Everything works again.


IMG_7666

I have a suspicion that we may see more of this as these trucks get older - I'll go pick up a couple more of these out of the junkyard, see about reworking them and keep them as spares.

 

[brillo_76]

Thanks for the update.. Glad you got it fixed.

Sent from my SM-A505U using Tapatalk